Group 1 elements which are a bit different from most other metals
Alkali metals
Relatively soft
Low densities
Low melting points
Much more reactive than other metals
React vigorously with water, oxygen and group 7 elements
As you go down the group
The elements become even more reactive
The melting points and boiling points decrease
Common table salt (sodium) doesn't suddenly catch fire when sprinkled on potatoes, unlike cesium
Reactivity
How easily atoms can lose or gain electrons and react with other atoms
Ionic compounds
Formed when a metal atom like sodium donates an electron to a non-metal like chlorine, creating oppositely charged ions that are attracted by electrostatic forces
Ionic compounds formed by alkali metals are generally white solids that dissolve in water to form colourless solutions
Reaction of alkali metals with water
1. Alkali metal + water → Metal hydroxide + Hydrogen gas
2. The reactions become more vigorous going down the group, with the hydrogen gas igniting
Reaction of alkali metals with chlorine
1. Alkali metal + Chlorine → Metal chloride salt
2. The reactions become more vigorous going down the group
Reaction of alkali metals with oxygen
Lithium + Oxygen → Lithium oxide
Sodium + Oxygen → Sodium oxide or Sodium peroxide
Potassium + Oxygen → Potassium peroxide or Potassium superoxide
You don't need to know why the particular oxide compounds form, just memorize them
The reactivity series is the relative ability of elements to displace other elements from their compounds.
In general, as we go down the periodic table, atoms get bigger and have lower ionisation energies so they are less reactive
Alkali metals are very reactive because they lose an electron easily due to having low ionisation energy
